A bit of background: lactose intolerance is actually the ancestral human trait; European hunter-gatherers more than 10,000 years ago did not have genes for lactase persistence (LP; lactase is the enzyme which digests lactose, and in non-lactose tolerant populations it is lost soon after weaning) into adulthood. However, some genes for LP spread across a large area among diverse populations very quickly around 5,000-10,000 years ago. It's common throughout non-Sub-Saharan Africa, Europe, the Middle-East and India today, although I think it's not that common in Mediterranean populations (Greeks, Italians, Mediterranean Middle-East, Southern French, Balkans) compared to more inland populations. More info on Wikipedia.

I couldn't really find much info online about lactose tolerance in Tibetan populations.

All I've found so far is this PhD Dissertation. It says that there is some evidence that Tibetans have higher lactase persistence although the abstract at least doesn't cite any sources. Traditional Tibetan diets contain more dairy than traditional Chinese diets, but that in itself cannot be used as an indicator of lactase persistence. The abstract goes on to describe how Tibetans actually don't have the same alleles for lactase persistence that exists in surrounding populations (not described but in this case, probably South Asians).

Lactose absorption capacity was examined in 641 apparently healthy adolescents and adults (447 males and 194 females with an average age of 22.9 years and an age range of 16-46 years) using a field version of the lactose tolerance test with breath hydrogen determination. In the total sample, 89 lactose absorbers and 552 lactose malabsorbers were identified. Lactose malabsorption was most frequent in a subgroup of Han (Chinese) from northeastern China (229 of 248 subjects, 92.3%). Among 198 Mongols from Inner Mongolia, there were 174 lactose malabsorbers (87.9%). The frequency of lactose malabsorption was lowest in a group of Kazakhs, traditional herders from the northwestern region of Xinjiang (149 of 195 subjects, 76.4%). Reported symptoms of lactose intolerance were significantly more frequent in lactose malabsorbers. The findings in northern Han are similar to the reported lactose malabsorption frequency in southern (mainly overseas) Chinese, and correspond with the absence of animal milk from traditional Chinese diets. The relatively low prevalence of lactose malabsorption among the Kazakhs suggests that lactose persistence may be frequent in herding pastoralist populations of southwest Asia.

This study actually tested for lactose digestion using a hydrogen breath test. It indicated that Mongols and Kazakhs actually [i]don't[/url] digest lactose that well, compared to Northern Europeans or Indians. I found this quite interesting, since obviously they historically did consume a lot of milk. I have a feeling that Tibetans would give similar results too, but I may be wrong, hopefully a similar study is conducted.

This raises a few questions for me.

Do the traditional preparations of milk in Central Asian nomadic populations remove lactose in some way?

I know Mongolians and Turkic people have a fermented horse milk beverage that removes lactose, but then they don't drink that all the time do they?

Tibetans and Mongolians have "milk tea" beverages, but thinking about it, the Tibetan version actually uses butter instead of milk right? Butter is just milk fats without lactose.

Is raw milk actually drunk in Tibet traditionally?

I remember reading somewhere that in populations that have a relatively lower frequency of LP but still rear cattle, dairy is still taken, but prepared in a way that removes or reduces the lactose (cheese, yogurt, kefir). I can't find the source at the moment though. Do Tibetans usually consume dairy in this way?

I probably don't have LP genes too. I don't usually drink milk anyway, but recently I was eating ricotta cheese regularly. It gave me a bad outbreak of acne. I stopped and the acne has been gradually going away. I sometimes take whey protein too, which did not give me as bad a reaction as when I was taking ricotta. I took ricotta because I thought because it would be fine because it was made of whey anyway. (Whey is the most bioavailable form of protein) I think now that I was wrong, because ricotta production is basically based on the remaining whey liquid which contains all the lactose that is removed from normal cheese. Basically a super-charged lactose bomb. I ate it with berries, it tasted good, but it also made me bloated afterwards, sometimes feeling like puking even.